<template>
  <div class="s-canvas">
    <canvas
      id="s-canvas"
      :width="contentWidth"
      :height="contentHeight"
    ></canvas>
  </div>
</template>
<script>
export default {
  name: 'Identify',
  props: {
    identifyCode: {
      type: String,
      default: 'asdf'
    }
  },
  data() {
    return {
      fontSizeMin: 36,
      fontSizeMax: 50,
      backgroundColorMin: 180,
      backgroundColorMax: 240,
      colorMin: 50,
      colorMax: 160,
      lineColorMin: 48,
      lineColorMax: 50,
      dotColorMin: 0,
      dotColorMax: 255,
      contentWidth: 128,
      contentHeight: 48
    }
  },
  methods: {
    // 生成一个随机数
    randomNum(min, max) {
      return Math.floor(Math.random() * (max - min) + min)
    },
    // 生成一个随机的颜色
    randomColor(min, max) {
      let r = this.randomNum(min, max)
      let g = this.randomNum(min, max)
      let b = this.randomNum(min, max)
      return 'rgb(' + r + ',' + g + ',' + b + ')'
    },
    drawPic() {
      let canvas = document.getElementById('s-canvas')
      let ctx = canvas.getContext('2d')
      // ctx.textBaseline = 'bottom'
      // 绘制背景
      ctx.fillStyle = this.randomColor(
        this.backgroundColorMin,
        this.backgroundColorMax
      ) //图形填充颜色设置
      ctx.strokeStyle = this.randomColor(
        this.backgroundColorMin,
        this.backgroundColorMax
      ) //图形轮廓的颜色设置
      ctx.fillRect(0, 0, this.contentWidth, this.contentHeight) //绘制一个填充的矩形 0 0 width height x起点 y起点  宽 高
      ctx.strokeRect(0, 0, this.contentWidth, this.contentHeight) // 绘制一个矩形边框 0 0 width height x起点 y起点  宽 高
      // ctx.clearRect(50,0,this.contentWidth,this.contentHeight)  //清除指定矩形区域，清除部分完全透明
      // 绘制文字
      for (let i = 0; i < this.identifyCode.length; i++) {
        this.drawText(ctx, this.identifyCode[i], i)
      }
      this.drawLine(ctx)
      this.drawDot(ctx)
    },
    drawText(ctx, txt, i) {
      ctx.fillStyle = this.randomColor(this.colorMin, this.colorMax)
      ctx.font =
        this.randomNum(this.fontSizeMin, this.fontSizeMax) + 'px SimHei' //字体大小
      ctx.textBaseline = 'alphabetic' //基线对齐
      let x = (i + 1) * (this.contentWidth / (this.identifyCode.length + 1))
      let y = this.randomNum(this.fontSizeMax, this.contentHeight - 5)
      var deg = this.randomNum(-45, 45)
      // 修改坐标原点和旋转角度
      ctx.translate(x, y) //移动不同位置  参数偏移量
      ctx.rotate((deg * Math.PI) / 180) //旋转 参数角度
      ctx.fillText(txt, 0, 0)
      // 恢复坐标原点和旋转角度
      ctx.rotate((-deg * Math.PI) / 180)
      ctx.translate(-x, -y)
    },
    drawLine(ctx) {
      // 绘制干扰线
      for (let i = 0; i < 8; i++) {
        ctx.strokeStyle = this.randomColor(this.lineColorMin, this.lineColorMax)
        ctx.beginPath() //新建一条路径
        ctx.moveTo(
          this.randomNum(0, this.contentWidth),
          this.randomNum(0, this.contentHeight)
        ) //设置起点x,y
        ctx.lineTo(
          this.randomNum(0, this.contentWidth),
          this.randomNum(0, this.contentHeight)
        ) //绘制直线 x,y 一条当前位置到x,y点的直线
        ctx.stroke() // 通过线条绘制图形轮廓
        // ctx.closePath() //结束闭合路径
      }
    },
    drawDot(ctx) {
      // 绘制干扰点
      for (let i = 0; i < 100; i++) {
        ctx.fillStyle = this.randomColor(0, 255)
        ctx.beginPath()
        // 绘制圆弧或圆，x,y,radius，startAngle,endAngle,anticlockwise // x,y 圆心点，radius 半径，从startAngle开始到endAngle结束
        ctx.arc(
          this.randomNum(0, this.contentWidth),
          this.randomNum(0, this.contentHeight),
          1,
          0,
          2 * Math.PI
        )
        ctx.fill() //通过填充路径的内容区域生成实心的图形。
      }
    }
  },
  watch: {
    identifyCode() {
      this.drawPic()
    }
  },
  mounted() {
    this.drawPic()
  }
}
</script>
